The present invention relates to security seals and more particularly to security seals of the padlock type that include means for providing visual evidence of tampering.
Security seals of the padlock type are generally well known, and they have found wide spread use as a means for sealing structures such as currency bags, closures, electric meters, and the like. Examples of such seals may be found in the following U.S. Pat. Nos.: 3,375,033; 3,485,521; 4,278,281; 4,353,583 and 4,687,240. All of these seals generally have a plastic body with a pair of spaced cavities and a U-shaped shackle having ends that are permanently locked in the cavities when the seals are used. A number of these prior art seals have been designed to produce a visual indication of tampering. For example, in U.S. Pat. No. 4,687,240, the seal body is made of a pigmented plastic of a type which produces a white blush when deformed. If tampering occurs, the shackle deforms the plastic body to produce a milky white appearance that is readily visible. Additionally, because the shackle has sharp ends to deform the plastic, the shackle ends will, in some cases, protrude from the seal body giving an added visual indication of tampering. Other examples of visual indicators may be found in the above cited prior art.
As can be seen from these prior art references, those concerned with the development of security seals have long recognized the need for improvements in means that provide visual evidence of tampering. Other attempts at such improvements in non-padlock type security seals include the use of a dye that will seep from the seal onto the surrounding structures when tampering occurs. Examples of such prior art devices may be found in the following U.S. patents: U.S. Pat. Nos. 3,991,594; 3,463,532; and 4,326,741. These patents generally describe security seals having a chamber in which a dye is stored. When the chamber is penetrated the dye is ejected. As such, the dye will stain the outer surface of the tubing and/or stain the surrounding structures and even the hands of the person tampering with the tube. The advantages of such dye filled security seals are numerous. One such advantage being that it becomes easier to determine, even from substantial distances, that the seal has been compromised. More important, such dyes can provide on-site evidence that tampering has occurred plus evidence of the person or tools used to effect the tampering.
One of the most critical problems confronting developers of such seals has been the overall cost of producing, shipping, and using such seals. The padlock type security seal has long been recognized as one of the most economical and practical solutions to the design of seals in general. Such seals are easy to operate and are not susceptible to accidental breakage during use. The present invention retains most of the advantages of such prior art padlock type seals while also providing an inexpensive, highly reliable, versatile means of providing visual evidence of seal tampering.